E-portfolio for teknik asas mikrobiologi: Eportfolio week 9

This week I have done two experiment which are experiment 12 and experiment 13. Experiment 12 is on Nutritional Requirements: Media for the Routine Cultivation of Bacteria while Experiment 13 is on the Use of Differential, Selective, and Enriched Media. For experiment 12, the procedures are as followed. We first inoculate the microorganisms (E. coli, A. faecalis and S.mitis) to different media ( yeast extract broth, nutrient broth, glucose broth and inorganic synthetic broth in four test tubes respectively by using Mohr pipette. After inoculate the broth culture and incubate the culture for 24 to 48 hours, we use the spectrophotometer to measure the optical density readings with the wavelength of 600nm. First, we measure the blank of culture, then we only measure the optical density for different media containing different microorganisms.

For experiment 13, we do the experiment by following the procedures. We label the cover of the plate properly and divide each of the Petri dishes into the required number of section by marking the bottom of the dishes. Each section are labelled with the name of the organism to be inoculated. Using aseptic technique, we inoculate all plates, except the blood agar plate, with the designated organisms by making a single line of inoculation of each organism in its appropriate section. Using aseptic techniques, we inoculate the blood agar by making a single line of inoculation. On completion of each single line of inoculation, we use the inoculating loop and make three or four stabs at a 45 degree angle across the streak.

We inoculate each of the different media with the following:
a) Phenylethyl alcohol agar: E.coli, S. aureus, and E. faecalis.
b) Crystal violet agar: E. coli, S.aureus, and E. faecalis.
c) 7.5% sodium chloride agar: S. aureus, S. epidermidis and E. coli
d) Mannitol salt agar: S. aureus, S.epidermidis, E. aerogenes. and E.coli
e) MacConkey agar: E. coli, E. aerogenes, S. typhrimurium, and S. aureus
f) Eosin-methylene blue agar: E. coli, E. aerogenes, S. typhimurium, and S. aureus
g) Blood agar: E. faecalis, S. mitits, and Streptococcus pyogenes.

The phenyethyl alcohol agar plate was incubated in an inverted position for 48 to 72 hours at 37 degree celcius while the remaining plates were incubated in an inverted position for 24 to 48 hours at 37 degree celcius.

The other day, we examine each plate and recorder the result according to the amount of growth along line of inoculation, appearance of the growth and the change in appearance of the medium surrounding the growth.

The purpose of this experiment is to understand which medium is suitable to culture which microorganisms.

The picture of the spectrophotometer